The present invention relates to an electrochemical device and a method for the preparation thereof.
Since the time of Industrial Revolution in the nineteenth century, fossil fuels, such as gasoline, kerosene, coal, or the like, have been used not only as an energy source for vehicles, but also as an energy source for power generation. Fossil fuels have allowed the human race to enjoy many benefits such as a higher standard of living, advances in industrial development, and the like. However, continued use of fossil fuels risks severe environmental destruction. Furthermore, there exists fear and uncertainty over the possibility of the depletion of fossil fuel sources, so much so that the stable supply of fossil fuels over the long term is in question.
Hydrogen is contained in water and exists abundantly on the earth, and since it has a large chemical energy contained per unit weight and, in use as an energy source, does not emit noxious gases or gases possibly contributing to global warming, it is desirable as an energy source, one which is clean and moreover plentiful in supply.
Research advances relating to a fuel cell, capable of recovering electrical energy from hydrogen continue to be developed. In this regard, expectations are high for the application of fuel cells to large scale power generation, on-site self-generation of power, a power source for an electric vehicle, or the like.
Typically, an electrical energy generating device for gathering electrical energy from hydrogen (i.e., a fuel cell) can include a hydrogen electrode, fed with hydrogen, and an oxygen electrode, fed with oxygen. Hydrogen fed to the hydrogen electrode is dissociated into a proton and electrons, by a catalytic action, with the electrons being collected by a current collector of the hydrogen electrode. The proton is transported towards the oxygen electrode. The electrons fed to the hydrogen electrode are transported through a load to the oxygen electrode. Meanwhile, oxygen fed to the oxygen electrode is bound to the proton and to the electrons, transported from the hydrogen electrode, to generate water. Thus, an electromotive force is produced between the hydrogen and oxygen electrodes thereby causing current to flow in the load.
In order to produce an electromotive force across the hydrogen and oxygen electrodes, hydrogen needs to be dissociated into the proton and electrons on the hydrogen electrode, while the proton, electrons and oxygen must react on the oxygen electrode to yield water. Thus, a catalytic layer for promoting dissociation of the proton and the electrons of hydrogen is needed in the hydrogen electrode, while a catalytic layer for promoting the linkage of the proton, electrons and oxygen is needed in the oxygen electrode.
The catalytic layers bring about the aforementioned action by contacting with hydrogen in the hydrogen electrode, and by contacting with oxygen in the oxygen electrode. Thus, in order for the catalytic layers to operate effectively, the catalyst contained in the catalytic layer needs to contact efficiently with hydrogen or oxygen. Thus, if the contact efficiency between the catalyst contained in the catalytic layer and the hydrogen or oxygen is low, the catalytic action achieved is insufficient in comparison with the amount of the catalyst used.
The aforementioned problem concerning energy inefficiency occurs not only in the hydrogen or oxygen electrodes of a typical fuel cell, but also in a gas diffusion electrode used in other typical electrochemical devices, such as an air cell, or the like.